1. Technical Field
The present invention relates to a transflective liquid crystal device having a reflecting display mode function and a transmitting display mode function.
2. Related Art
Conventionally, a transflective liquid crystal display device having a reflecting display mode function and a transmitting display mode function is known. In each pixel of a liquid crystal panel used for such a liquid crystal display device, a reflecting layer that reflects incident light from a viewing side is provided. Further, in each reflecting layer, an opening that transmits incident light from a backlight provided on a back surface side of the liquid crystal panel is provided. Furthermore, by overlapping a color filter on the reflecting layer, a color display can be achieved.
By the way, when a color display is performed through such a transflective liquid crystal display device, during the reflecting display mode, incident light from a viewing side passes through a color filter twice until the incident light is reflected by the reflective layer to be transmitted toward the viewing side. On the other hand, during the transmitting display mode, the incident light from the backlight passes through the color filter only once until the incident light is transmitted toward the viewing side. For this reason, the brightness of an image in the reflecting display mode is lower than the brightness of an image in the transmitting display mode. Further, the saturation of the image in the transmitting display mode is lower than the saturation of the image in the reflecting display mode.
In order to solve these problems, various technologies have been suggested. For example, a conventional art disclosed in Japanese Unexamined Patent Application Publication No. 2003-122273 has a configuration that only a part of a reflecting surface of a reflecting layer provided in every pixel is covered with a color filter. According to this configuration, since a part of the incident light from a viewing side is reflected without passing through a color filter, the brightness of an image increases and the saturation of the image decreases in the reflecting display mode. As a result, it is possible to eliminate the difference in the brightness and the difference in the saturation of the image between the reflecting display mode and the transmitting display mode.
Recently, the use of mobile phones having a built-in transflective liquid crystal display device has been widely spread. Most of the mobile phones are constructed such that while an operating button is operated, a backlight is turned on to perform a transmitting display mode, and while the operating button is not operated for a predetermined time, the backlight is turned off to be in a reflecting display mode. As a result, it is possible to display an image having high visibility during operation and to suppress power consumption during stand-by state. However, since the area of an opening in most of such mobile phones is determined by taking a serious view of the brightness of display in the transmitting display mode, the images in the reflecting display mode have a low visibility as compared to the transmitting display mode. As shown in FIG. 4, while the power is on, on the screen of the mobile phone, images displaying information such as date, time and battery level, which are useful for a user even during the stand-by state, are always displayed. Nevertheless, when the display mode of the mobile phone is changed to a reflecting display mode, the screen of the mobile phone becomes dark. As a result, it is difficult to view the images. Although the brightness of the images in the reflecting display mode can be improved by using a technology disclosed in Japanese Unexamined Patent Application Publication No. 2003-122273, a sufficient brightness of the images in the transmitting display mode cannot be obtained.
Accordingly, the present invention is designed to solve the above-mentioned problems, and it is an object of the present invention to provide a transflective liquid crystal display device capable of improving the visibility of an image in the reflecting display mode while ensuring a sufficient visibility of the image in the transmitting display mode.